The doctrine of the Trinity has a core teaching that was taught by the early church. The early church taught that Christ was begotten before eternity. This is a necessary and scriptural teaching of the nature of Christ. Christianity teaches that Christ is fully God and Fully man.
When discussing Christs divinity, the early church fathers taught that Christ was begotten before time and creation. The early church fathers explained that Christ is the Word of God and that there is no time when God did not speak. Christ is the radiance of the Father. Similar to the Sun emitting light. Metaphorically speaking and not literally, the Father is the Sun and Christ is the radiance that comes from the sun. Christ is generated or begotten from the father eternally. There is no time when the Son was not generated from the Father similar to the sun always emitting light. Below are quotes from the early church fathers on this teaching.
Ignatius a.d. 30–107
He (Jesus Christ), being begotten by the Father before the beginning of time, was God the Word, the only-begotten Son, and remains the same for ever; for “of His kingdom there shall be no end,” says Daniel the prophet.
The Epistle of Ignatius to the Magnesians Chapter VI.—Preserve harmony.
But our Physician is the only true God, the unbegotten and unapproachable, the Lord of all, the Father and Begetter of the only-begotten Son. We have also as a Physician the Lord our God, Jesus the Christ, the only begotten Son and Word, before time began, but who afterwards became also man, of Mary the virgin. For “the Word was made flesh.” Being incorporeal, He was in the body; being impassible, He was in a passible body; being immortal, He was in a mortal body; being life, He became subject to corruption, that He might free our souls from death and corruption, and heal them, and might restore them to health, when they were diseased with ungodliness and wicked lusts.
Epistles to the Ephesians Chapter VII.—Beware of false teachers
Justin Martyr a.d. 110–165
“I shall give you another testimony, my friends,” said I, “from the Scriptures, that God begat before all creatures a Beginning, [who was] a certain rational power [proceeding] from Himself, who is called by the Holy Spirit, now the Glory of the Lord, now the Son, again Wisdom, again an Angel, then God, and then Lord and Logos; and on another occasion He calls Himself Captain, when He appeared in human form to Joshua the son of Nave (Nun). For He can be called by all those names, since He ministers to the Father’s will, and since He was begotten of the Father by an act of will; just as we see happening among ourselves: for when we give out some word, we beget the word; yet not by abscission, so as to lessen the word [which remains] in us, when we give it out: and just as we see also happening in the case of a fire, which is not lessened when it has kindled [another], but remains the same; and that which has been kindled by it likewise appears to exist by itself, not diminishing that from which it was kindled.
The Word of Wisdom, who is Himself this God begotten of the Father of all things, and Word, and Wisdom, and Power, and the Glory of the Begetter, will bear evidence to me, when He speaks by Solomon the following: ‘If I shall declare to you what happens daily, I shall call to mind events from everlasting, and review them. The Lord made me the beginning of His ways for His works. From everlasting He established me in the beginning, before He had made the earth, and before He had made the deeps, before the springs of the waters had issued forth, before the mountains had been established. Before all the hills He begets me. God made the country, and the desert, and the highest inhabited places under the sky. When He made ready the heavens, I was along with Him, and when He set up His throne on the winds: when He made the high clouds strong, and the springs of the deep safe, when He made the foundations of the earth, I was with Him arranging. I was that in which He rejoiced; daily and at all times I delighted in His countenance, because He delighted in the finishing of the habitable world, and delighted in the sons of men.
Dialogue of Justin, Philosopher and Martyr, with Trypho, a Jew Chapter LXI—Wisdom is begotten of the Father, as fire from fire.
Theophilus of Antioch a.d. 115–168–181
You will say, then, to me: “You said that God ought not to be contained in a place, and how do you now say that He walked in Paradise?” Hear what I say. The God and Father, indeed, of all cannot be contained, and is not found in a place, for there is no place of His rest; but His Word, through whom He made all things, being His power and His wisdom, assuming the person of the Father and Lord of all, went to the garden in the person of God, and conversed with Adam. For the divine writing itself teaches us that Adam said that he had heard the voice. But what else is this voice but the Word of God, who is also His Son? Not as the poets and writers of myths talk of the sons of gods begotten from intercourse [with women], but as truth expounds, the Word, that always exists, residing within the heart of God. For before anything came into being He had Him as a counsellor, being His own mind and thought.
But when God wished to make all that He determined on, He begot this Word, uttered, the first-born of all creation, not Himself being emptied of the Word [Reason], but having begotten Reason, and always conversing with His Reason. And hence the holy writings teach us, and all the spirit-bearing [inspired] men, one of whom, John, says, “In the beginning was the Word, and the Word was with God,” showing that at first God was alone, and the Word in Him. Then he says, “The Word was God; all things came into existence through Him; and apart from Him not one thing came into existence.” The Word, then, being God, and being naturally produced from God, whenever the Father of the universe wills, He sends Him to any place; and He, coming, is both heard and seen, being sent by Him, and is found in a place.
Theophilus to Autolycus. Book II. Chapter XXII.—Why God is Said to Have Walked.
Origen a.d. 185–230–254
For we do not say, as the heretics suppose, that some part of the substance of God was converted into the Son, or that the Son was procreated by the Father out of things non-existent, i.e., beyond His own substance, so that there once was a time when He did not exist; but, putting away all corporeal conceptions, we say that the Word and Wisdom was begotten out of the invisible and incorporeal without any corporeal feeling, as if it were an act of the will proceeding from the understanding. Nor, seeing He is called the Son of (His) love, will it appear absurd if in this way He be called the Son of (His) will. Nay, John also indicates that “God is Light,” and Paul also declares that the Son is the splendour of everlasting light. As light, accordingly, could never exist without splendour, so neither can the Son be understood to exist without the Father; for He is called the “express image of His person,” and the Word and Wisdom.
How, then, can it be asserted that there once was a time when He was not the Son? For that is nothing else than to say that there was once a time when He was not the Truth, nor the Wisdom, nor the Life, although in all these He is judged to be the perfect essence of God the Father; for these things cannot be severed from Him, or even be separated from His essence. And although these qualities are said to be many in understanding, yet in their nature and essence they are one, and in them is the fulness of divinity. Now this expression which we employ—”that there never was a time when He did not exist”—is to be understood with an allowance. For these very words “when” or “never” have a meaning that relates to time, whereas the statements made regarding Father, Son, and Holy Spirit are to be understood as transcending all time, all ages, and all eternity. For it is the Trinity alone which exceeds the comprehension not only of temporal but even of eternal intelligence; while other things which are not included in it are to be measured by times and ages. This Son of God, then, in respect of the Word being God, which was in the beginning with God, no one will logically suppose to be contained in any place; nor yet in respect of His being “Wisdom,” or “Truth,” or the “Life,” or “Righteousness,” or “Sanctification,” or “Redemption:” for all these properties do not require space to be able to act or to operate, but each one of them is to be understood as meaning those individuals who participate in His virtue and working.
Origen De Principiis. Book IV Chapter I.—On the Inspiration of Holy Scripture, and How the Same is to be Read and Understood, and What is the Reason of the Uncertainty in it; and of the Impossibility or Irrationality of Certain Things in it, Taken According to the Letter Summary (of Doctrine) Regarding the Father, the Son, and the Holy Spirit, and the Other Topics Discussed in the Preceding Pages
Dionysius, Bishop of Alexandria a.d. 200–265
(From the First Book.)
1. There certainly was not a time when God was not the Father.
2. Neither, indeed, as though He had not brought forth these things, did God afterwards beget the Son, but because the Son has existence not from Himself, but from the Father.
(And after a few words he says of the Son Himself:—)
3. Being the brightness of the eternal Light, He Himself also is absolutely eternal. For since light is always in existence, it is manifest that its brightness also exists, because light is perceived to exist from the fact that it shines, and it is impossible that light should not shine. And let us once more come to illustrations. If the sun exists, there is also day; if nothing of this be manifest, it is impossible that the sun should be there. If then the sun were eternal, the day would never end; but now, for such is not really the state of the case, the day begins with the beginning of the sun, and ends with its ending. But God is the eternal Light, which has neither had a beginning, nor shall ever fail. Therefore the eternal brightness shines forth before Him, and co-exists with Him, in that, existing without a beginning, and always begotten, He always shines before Him; and He is that Wisdom which says, “I was that wherein He delighted, and I was daily His delight before His face at all times.”
(And a little after he thus pursues his discourse from the same point:—)
4. Since, therefore, the Father is eternal, the Son also is eternal, Light of Light. For where there is the begetter, there is also the offspring. And if there is no offspring, how and of what can He be the begetter? But both are, and always are. Since, then, God is the Light, Christ is the Brightness. And since He is a Spirit—for says He, “God is a Spirit” —fittingly again is Christ called Breath; for “He,” saith He, “is the breath of God’s power.” (And again he says:—)
5. Moreover, the Son alone, always co-existing with the Father, and filled with Him who is, Himself also is, since He is of the Father. The Works of Dionysius. Extant Fragments. Part I.—Containing Various Sections of the Works. IV.—Epistle to Dionysius Bishop of Rome.
Athanasius a.d. 298–373
As we said above, so now we repeat, that the divine generation must not be compared to the nature of men, nor the Son considered to be part of God, nor the generation to imply any passion whatever; God is not as man; for men beget passibly, having a transitive nature, which waits for periods by reason of its weakness. But with God this cannot be; for He is not composed of parts, but being impassible and simple, He is impassibly and indivisibly Father of the Son.
This again is strongly evidenced and proved by divine Scripture. For the Word of God is His Son, and the Son is the Father’s Word and Wisdom; and Word and Wisdom is neither creature nor part of Him whose Word He is, nor an offspring passibly begotten. Uniting then the two titles, Scripture speaks of ‘Son,’ in order to herald the natural and true offspring of His essence; and, on the other hand, that none may think of the Offspring humanly, while signifying His essence, it also calls Him Word, Wisdom, and Radiance; to teach us that the generation was impassible, and eternal, and worthy of God. What affection then, or what part of the Father is the Word and the Wisdom and the Radiance? So much may be impressed even on these men of folly; for as they asked women concerning God’s Son, so let them inquire of men concerning the Word, and they will find that the word which they put forth is neither an affection of them nor a part of their mind.
But if such be the word of men, who are passible and partitive, why speculate they about passions and parts in the instance of the immaterial and indivisible God, that under pretence of reverence they may deny the true and natural generation of the Son? Enough was said above to shew that the offspring from God is not an affection; and now it has been shewn in particular that the Word is not begotten according to affection. The same may be said of Wisdom; God is not as man; nor must they here think humanly of Him. For, whereas men are capable of wisdom, God partakes in nothing, but is Himself the Father of His own Wisdom, of which whoso partake are given the name of wise. And this Wisdom too is not a passion, nor a part, but an Offspring proper to the Father. Wherefore He is ever Father, nor is the character of Father adventitious to God, lest He seem alterable; for if it is good that He be Father, but has not ever been Father, then good has not ever been in Him.
Four discourses against the Arians Discourse I.28